Improve NetworkServiceTestCase._get_ip_flow_range() function

Improve the method to calculate the CIDR IP address range (first one,
last one). IPv4Network or IPv6Network hosts() is an iterator throught
the list of valid IPs. If the network is too big, the generation of a
list [1] can be very expensive.

[1]https://github.com/opnfv/yardstick/blob/master/yardstick/benchmark/scenarios/networking/vnf_generic.py#L90

JIRA: YARDSTICK-1339

Change-Id: I9352b2e7ff4925c246df8b40ecf43e8dc96c42d2
Signed-off-by: Rodolfo Alonso Hernandez <rodolfo.alonso.hernandez@intel.com>

1 files changed, 24 insertions, 25 deletions

diff --git a/yardstick/benchmark/scenarios/networking/vnf_generic.py b/yardstick/benchmark/scenarios/networking/vnf_generic.py
index 7a11d3e76..a7557733b 100644
--- a/yardstick/benchmark/scenarios/networking/vnf_generic.py
+++ b/yardstick/benchmark/scenarios/networking/vnf_generic.py
@@ -64,37 +64,36 @@ class NetworkServiceTestCase(scenario_base.Scenario):
         self._mq_ids = []
 
     def _get_ip_flow_range(self, ip_start_range):
+        """Retrieve a CIDR first and last viable IPs
 
-        # IP range is specified as 'x.x.x.x-y.y.y.y'
+        :param ip_start_range: could be the IP range itself or a dictionary
+               with the host name and the port.
+        :return: (str) IP range (min, max) with this format "x.x.x.x-y.y.y.y"
+        """
         if isinstance(ip_start_range, six.string_types):
             return ip_start_range
 
-        node_name, range_or_interface = next(iter(ip_start_range.items()), (None, '0.0.0.0'))
+        node_name, range_or_interface = next(iter(ip_start_range.items()),
+                                             (None, '0.0.0.0'))
         if node_name is None:
-            # we are manually specifying the range
-            ip_addr_range = range_or_interface
+            return range_or_interface
+
+        node = self.context_cfg['nodes'].get(node_name, {})
+        interface = node.get('interfaces', {}).get(range_or_interface)
+        if interface:
+            ip = interface['local_ip']
+            mask = interface['netmask']
         else:
-            node = self.context_cfg["nodes"].get(node_name, {})
-            try:
-                # the ip_range is the interface name
-                interface = node.get("interfaces", {})[range_or_interface]
-            except KeyError:
-                ip = "0.0.0.0"
-                mask = "255.255.255.0"
-            else:
-                ip = interface["local_ip"]
-                # we can't default these values, they must both exist to be valid
-                mask = interface["netmask"]
-
-            ipaddr = ipaddress.ip_network(six.text_type('{}/{}'.format(ip, mask)), strict=False)
-            hosts = list(ipaddr.hosts())
-            if len(hosts) > 2:
-                # skip the first host in case of gateway
-                ip_addr_range = "{}-{}".format(hosts[1], hosts[-1])
-            else:
-                LOG.warning("Only single IP in range %s", ipaddr)
-                # fall back to single IP range
-                ip_addr_range = ip
+            ip = '0.0.0.0'
+            mask = '255.255.255.0'
+
+        ipaddr = ipaddress.ip_network(
+            six.text_type('{}/{}'.format(ip, mask)), strict=False)
+        if ipaddr.prefixlen + 2 < ipaddr.max_prefixlen:
+            ip_addr_range = '{}-{}'.format(ipaddr[2], ipaddr[-2])
+        else:
+            LOG.warning('Only single IP in range %s', ipaddr)
+            ip_addr_range = ip
         return ip_addr_range
 
     def _get_traffic_flow(self):